Arena Raises $200 Million Series B at $3.1 Billion Valuation and Launches AI Alignment Index

Arena said it has raised a $200 million Series B at a $3.1 billion valuation, positioning the company behind the former LMArena project as a commercial evaluator of AI agents in real-world work. The round, co-led by Lightspeed Venture Partners and Khosla Ventures, arrives alongside the new Arena Alignment Index, a leaderboard meant to measure whether frontier agents act in line with user intent.